Objective: To provide an estimate of benefit, if any, of child restraint systems over seat belts alone for children aged from 2 through 6 years.

Design: Cohort study.

Setting: A sample of children in US passenger vehicle crashes was obtained from the National Highway Transportation Safety Administration by combining cases involving a fatality from the US Department of Transportation Fatality Analysis Reporting System with a probability sample of cases without a fatality from the National Automotive Sampling System.

Participants: Children in two-way crashes occurring between 1998 and 2003.

Conclusion: Based on these findings as well as previous epidemiological and biomechanical evidence for child restraint system effectiveness in reducing nonfatal injury risk, efforts should continue to promote use of child restraint systems through improved laws and with education and disbursement programs.